A common technique of making spring mattresses is the so-called pocket technique. This means that the springs are enclosed in pockets, i.e. they are individually enclosed by a casing material. In this way, the springs will be relatively individually resilient so that they can flex individually without affecting the neighboring springs and, thus, the comfort for the user increases since his weight will be distributed more uniformly over the surface that receives the load.
A known form of pocketed spring assembly comprises a plurality of parallel strings of springs joined together by gluing, clipping, welding or the like, thereby securing the strings of springs to each other. Each string of springs comprises a strip of fabric wrapped around a plurality of coil springs which are aligned in a row. The strings may extend in the mattress' width or length direction.
In order to create such a string of springs, a plurality of coil springs are aligned in a row and a strip of fabric is wrapped around the aligned row of coil springs so as to create two plies, one on either side of the row of springs. The edges of the strip of fabric are joined together with a longitudinal line of attachment extending longitudinally along the row of springs. The outermost edges of the strip of fabric are joined together with outermost transverse lines of attachment in order to prevent the outermost springs from falling out of the strip of fabric. Between adjacent coil springs transverse lines of attachment extend generally parallel to the axis of the coil springs, separating the strip of fabric into individual pockets, each pocket containing a coil spring.
However, lying directly on the pocket mattress is normally not comfortable, and in order to provide good sleeping and resting comfort, it is normally required to add a layer of padding or the like on top of the mattress. Such a padding layer is often assembled together with the pocket mattress, to form an encased upholstered mattress. Alternatively, a separate padding mattress may be laid loosely on top of the pocket spring mattress. A drawback of such an additional top layer is, however, that this reduces the individual resilience of the pocket units, and provides a less than optimal pressure distribution.
To this end, it has been proposed in EP1 330 171 to connect foam or other cushioning or padding materials to the top of each coil spring, and to encase each such unit of foam/padding and coil spring, within each individual pocket. This provides an additional padding layer which maintains the inherent individual resilience of the pocket spring mattress.
However, a drawback of this previously proposed mattress is that connection of the foam/padding to the coil spring is relatively complicated and costly to achieve. Further, there is a sever risk that the foam/padding will be deformed or disconnected, and e.g. be pushed into the convolutions of the coil spring. This will significantly deteriorate both the appearance and the comfort of the mattress.
There is a therefore a need for individual pocketed coil springs and a pocket spring mattress which is easier and/or less expensive to manufacture but which at the same time provides at least an equivalent comfort compared with other prior-art pocket mattresses. It is also a need for such individual pocketed coil springs and pocket spring mattresses that delivers improved resiliency and responsiveness and that enables the use of reduced amounts of cushioning or padding material on top of the bedding or seating product once the spring assembly is complete. Still further, there is a need for such individual pocketed coil springs and pocket spring mattresses that are more robust and which maintains their properties over a prolonged period of time and use.